This invention relates to the use of molybdenum trioxide as a catalyst for fluorinating certain chlorinated and/or brominated compounds. In particular, it relates to the reaction of benzotrichloride (BTC) or monochlorobenzotrichloride (MCBTC) with hydrogen fluoride (HF) in the presence of a molybdenum trioxide catalyst to make benzotrifluoride (BTF) or monochlorobenzotrifluoride (MCBTF), respectively.
BTF is an important commercial product used, inter alia, as a solvent, a lubricant, and a cleaning solution. It is made by reacting BTC with HF using a molybdenum pentachloride catalyst. See U.S. Pat. No. 4,098,832, herein incorporated by reference, for a detailed description of that reaction. While molybdenum pentachloride is called a "catalyst," it cannot be entirely recovered because it reacts to some extent with air and moisture to form oxyhalides; special precautions are therefore required to preserve it. Moreover, it is soluble in the product and is therefore difficult to separate from the product. It is also very expensive and there is only a single supplier.